1. Field of the Invention
The present invention relates to a recording apparatus, and more particularly, relates to a structure of an operation key which is provided in an exterior of the recording apparatus, and has a display part and an operation part.
2. Description of the Related Art
In information processing apparatuses, such as office computers, personal computers, and/or a word processors, display devices for displaying various information about a status of the apparatus have been conventionally used. Also in image recording apparatuses or image reading apparatuses such as printers, copying machines, printing devices, facsimile machines, and/or scanners, similar display devices have been used.
The display device is generally arranged in an exterior of the device where the display device is easily viewed. In recent years, as the information apparatuses are personalized, the size of the devices has become miniaturized and the prices of the devices have been reduced. The personal computer, the word processor, or the printer which is an output device for them have conventionally been used on a desktop. However, because of the recent miniaturization, these devices have become portable and can now be easily carried about. As a result, devices which can be driven by a battery have become more practical and prevalent.
On a display panel in the exterior of the devices, an illumination device is often provided which functions as a display device for notifying a user of operation status such as on/off of an operation key. In the illumination device, an end surface under a light guide (inside of the device) made of acrylic resin or the like is generally arranged opposite to a light emitting element such as a light emitting diode. Light enters through the end surface of the lower part of the light guide, and the light guide emits the light from an end surface on the opposite side. The end surface that emits the light forms a display part of the device. In an operation part of the device such as an operation key, around which the display part is arranged, a status of operation, for example, on/off, can be displayed.
FIGS. 10A to 10C are longitudinal sectional views illustrating a conventional display device. An opening 905 is formed in a panel 900 of an exterior, and an operation part (for example, an operation key) is formed within the opening 905. A circular member 850 for light shielding is arranged in an interior of a cylinder-shaped light guide 800. A circuit board 950 is arranged in an interior of the panel 900 and a light emitting diode 910 (i.e., a light emitting element) is mounted on the circuit board 950. The light emitting diode 910 is arranged under the center of the cylinder-shaped light guide 800. Radial light (light flux) 915 which is emitted from the light emitting diode 910 enters through a lower part of the light guide 800. The incident light is repeatedly refracted and reflected in a light guiding part in the light guide 800, and reaches a display part 810 at an upper end. As a result, the light which reaches the display part 810 can be viewed by a user. The display part 810 displays the on/off state of the operation part (operation key). In the display part 810, as the amount of the light that reaches the display part 810 increases, the visibility increases accordingly.
FIGS. 10A to 10C further illustrate varying states of optical paths when a distance between a lower end 820 of the light guide 800 and the light emitting diode 910 varies in an axis direction (a height direction) to P, 2×P, and 3×P. As illustrated in FIG. 10A, if the distance between the light guide 800 and the light emitting diode 910 is P which is relatively short distance, the number of reflection times in the light guide 800 is large, and the amount of light that reaches the display part 810 is relatively small. As illustrated in FIG. 10B, if the distance is set to 2×P which is twice as long, the number of reflection times in the light guide 800 decreases, and the amount of light that reaches the display part 810 increases. Further, as illustrated in FIG. 10C, if the distance is set to 3×P which is three times as long, the number of reflection times in the light guide 800 further decreases, and the amount of light that reaches the display part 810, further increases.
FIG. 11 is a longitudinal sectional view illustrating another conventional display device. In lower portions of the cylindrical light guide 800, a plurality of the light emitting diodes 910 are arranged along a circular lower end of the light guide 800. The structure illustrated in FIG. 11 is different from the structure illustrated in FIG. 10 in this respect, however, in other respects, the structure of FIG. 11 is otherwise similar to FIG. 10. In the structure illustrated in FIG. 10, the number of reflection times in the light guide 800 is decreased and the amount of the light that reaches the display part 810 is increased in order to increase the visibility. For that purpose, the distance between the light guide 800 and the light emitting diodes 910 has to be large as illustrated in FIGS. 10B and 10C. As a result, it is not possible to achieve both the improvement of the visibility and slimming-down of the display device at the same time.
In the structure illustrated in FIG. 11, by reducing the number of reflection times in the light guide 800, the above-described disadvantage of the structures illustrated in FIGS. 10A to 10C can be eliminated. That is, even in a case where the distance between the light guide 800 and the light emitting diode 910 is short, by reducing the number of reflection times in the light guide 800, the amount of the light that reaches the display part 810, can be sufficiently ensured. However, in the structure illustrated in FIG. 11, because the plurality of light emitting diodes 910 are necessary in one display part 810, the cost and the power consumption of the device increase. For example, in a battery-operated printer, the increase of the power consumption shortens operating time of the printer.